A tanker comprising a detachable mooring buoy is known from U.S. Pat. No. 4,604,961. The known tanker comprises a turret that can be connected to a mooring buoy by means of a mooring recess in the moonpool of the vessel. The known system has as a disadvantage that for a reliable connection of the buoy to the mooring recess, the contact surfaces must be accurately matched and be machined to a high degree of precision. Furthermore, no water tight seal is established, such that the space near the connecting interface of the vessel and the buoy will be below water level.